A site dedicated to information and discussion about the history of aviation and aeroplanes in Japan and the Far East.
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Friday, 20 July 2012

Taisho Airfield, the 101st Sentai and the Air Defence of Japan

An interesting thread at j-aircraft.com about the Ki-84 (Hayate) aircraft of the 101st Sentai included a photograph said to be taken at Taisho airfield at the end of the war. This shows a Ki-84 of the 101st, another of the 73rd, an unidentified Ki-45 Toryu, a Ki-61 Hien, a Ki-46 and a Ki-102 with an apparently unusual and unidentified tail marking.

Taisho, now Yao airport near Osaka, was the HQ of the 11th Air Division and remained so until the end of the war. It incorporated an air defence command and control centre. Although moves were put in place to move this to Osaka castle they were resisted and eventually cancelled, the centre remaining at Taisho until the end of the war. Taisho also deployed "rocket-type grenade launchers" for air defence but what these actually were is obscure - possibly a version of the 70mm barrage mortar that fired a shell with a barometric fuse that dispersed multiple parachute bombs with time fuses. The 11th also deployed an airborne Special Intelligence Squadron that monitored enemy air radio traffic in order to plot B-29 raids and it pioneered the use of the Ki-46 recce aircraft to detect and track incoming B-29 raids in conjunction with a combination of coastal radar stations and observer posts, both on land and on sea. The Ki-46s patrolled defined air defence sectors in formations of three aircraft and once a B-29 formation was sighted it would be shadowed and reported in real time by one of the aircraft, the others remaining within their sector to continue their patrol.

Radar alone was found insufficient to determine the direction of a raid unless it was accompanied by other information. Sometimes it was possible for the approximate course of the raid to be plotted by collating information from radar stations at Omaezaki, Nakiri, Shio no Misaki and Ashizuri Mizaki but because of locations and distances involved it was seldom simultaneous. As a result advance warning information networks were established with units on the Bonin Islands and Iwo Jima via GDC agencies in Tokyo transmitted to Eastern Army Command and direct from the Izu Islands, as well as improving plotting instrumentation in the radar stations at Omaezaki, Shirahama, Yawatahama and Osaka. The Special Intelligence Squadron specialised in the airborne monitoring of radio transmissions originating in Saipan and Tinian and also intercepted radio communications between enemy aircraft, with excellent results, this data being fed into the command and control centre. The centre was equipped with a one kw air-ground radio station operated by the 13th Air-Ground Radio Unit which was capable of broadcasting simultaneously to all airborne air defence aircraft. An element of the 13th was also assigned to each Sentai under command to further co-ordinate air-ground radio. In addition Central Army Command deployed two specialist air-ground radio aircraft in the Osake-Kobe area to assist in the direction of local air defence response.

The 23rd Air Brigade came under the command of the 11th Air Division as did the 246th Sentai which at one stage was the parent unit for the 16th IFC and later 82nd IFC. This latter unit deployed the Ki-46 in both the air defence reconnaissance and high-altitude interceptor roles. The 246th also specialised in the nocturnal deployment of single seat fighter aircraft adopting a similar technique to the Luftwaffe 'wilde sau' method and the use of Ta-dan air-to-air bombing. By the end of the war the 101st and 103rd Sentai were brigaded together as part of the 'mobile' air defence forces in the 100th Air Brigade headquartered at Takamatsu on Shikoku Island. The 101st was also at Takamatsu with the Brigade HQ but the 103rd was reported to be at Miki, west of Kobe and at Yura on Awaji Island. The 100th Air Brigade had originally included the 102nd Sentai but that was disbanded on 10th July 1945 after operations around Okinawa and its personnel were transferred to the 101st and 103rd.

When Nakajima began factory painting the Ki-84 in late 1944 there was some discussion about painting the aircraft in the Navy colours of D1 over J3 in order to participate in mobile force operations in support of the special attack operations. Eventually it was decided to paint the aircraft in the standard colours of # 7 olive brown over # 1 grey-green. Prior to this the Ki-84 was being issued in natural metal finish and painted (or not) at the Army depots in a dark green, the under surfaces remaining in natural metal. The dark green applied in these circumstances probably varied but a surviving 102nd Sentai rudder reveals a dark blueish-green paint colour like # 27 (青緑色 - ao midori iro - blue green colour) which has often been depicted as blue. Perhaps more than coincidentally the 102nd was engaged in special attack (Tokubetsu kôgeki) operations around Okinawa and photographs of the unit's aircraft show them equipped with a mixed bomb and drop tank load. Other Ki-84 artifacts recovered from the Philippines reveal a similar dark blueish-green paint which suggests that # 27 over natural metal is a viable choice for a model representing a Ki-84 prior to the commencement of factory painting. It is sometimes quite difficult to determine from photographs whether the under surfaces are in oxidised natural metal or painted but there are other clues including context, date and location, as well as minor painting details beyond the scope of this blog post. The popular depiction of Ki-84 models in dark "IJA" green with grey-green under surfaces is an unlikely combination. Most of the hobby paint generic "IJA" and "Nakajima" greens are closer to the slightly more olive # 21 (緑色 - midori iro) in appearance rather than the dark blueish-green # 27, but neither are really representative of the later # 7 which varied from a deep olive brown to a khaki colour. A rule of thumb for Ki-84 models therefore is either dark green over natural metal or olive brown over grey-green depending on unit, location and date.

Both Minoru Akimoto, Dr Yasuho Izawa and Japanese Army Wings suggest that the 101st tail marking did not incorporate any Chutai colour distinctions, those being restricted to painted spinners, but the Taisho photograph does seem to show differences in tone on the marking's components when compared to other images. The 101st is well known for its eleven aircraft 16th July 1945 dusk attack on US airfields at Yontan and Kadena on Okinawa as part of the Dai 3 Kikusui Sakusen preparations. Instructions were given to paint aircraft used in dawn and dusk special attack operations 鈍色 (Nibi iro - which means dull colour, but also sometimes dark grey) but it is not known whether the 101st Ki-84 were specially painted for this operation or not. In the past several Ki-84 special attack Shinbu tai ("stirring the martial spirit" units) have been depicted painted black, dark grey and even dark brown

Yao airport now has Two Japanese Ground Self Defense Force units in residence, the Chubu Herikoputatai with Fuji UH-1H/UH-1J and Kawasaki OH-6D and the III Hikotai (Squadron) with Fuji UH-1J and Kawasaki OH-6D. Several small carriers offer sightseeing and charter flights from Yao, including Asahi Airlines and Hankyu Airlines.

A Member of PAHWA

PAWHA is an international organisation representing a collective of researchers and authors from all walks of life, who collaborate with each other on their niche expertise in all areas and specialties of the Pacific war. Its alumni include about 50 members, mainly recognised authors and researchers. As multinational historians PAWHA members preserve a unanimous desire for objectivity and veritas. The PAWHA insignia represents the Southern Cross, signifying the skies of the Pacific. It was designed by Don Marsh.

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I first became fascinated by aviation in the Far East at the age of about 7 when my father lifted me into the cockpit of an 'Ohka' rocket-propelled piloted suicide bomb displayed outside the armoury at RAF Cottesmore. It made me think about the people who had designed and built such a weapon . . . and why . . . but especially those who were prepared to fly it - and those who had to face it.